![]() Scanning electron microscopy (SEM) of the SnSe powder and the thermally evaporated SnSe thin films (Figure 2) show con- trasting morphologies. These preferred orientation planes and the thinness of the thermally evaporated films explain the absence of peaks in the film which are shown in the powder. XRD of thinner films ( Figure S2b, Supporting Information) also shows a preferred (111) orientation, indicating that this preferred orientation post thermal evaporation may be a result of energetic interactions with the glass substrate. The Lotgering factors (see Equations (S1) and (S2) in the Supporting Information) for these peaks are 0.51 and 0.25, respectively, indicating preferred orienta- tion along these planes on the substrate (in particular the (111) plane) which is the plane of measurement for Seebeck, electrical, and thermal conductivity. While the SnSe powder diffraction pattern observed is similar to cold pressed SnSe powder, the thermally evaporated thin film has much larger (111) and (011) peak intensities compared to the other peak intensities. ![]() The peaks in these pat- terns can be assigned to the low temperature orthorhombic phase of SnSe which belongs to the pnma space group (crystal- lography open database file number 1537675). To confirm the SnSe film, an X-ray diffraction (XRD) pattern for the SnSe powder (fully assigned in Figure S2a in the Sup- porting Information) and for a typical thermally evaporated SnSe thin film are shown in Figure 1. Such a low thermal conductivity is of use for the development of thermoelectric generators, but is also of interest to the development of other SnSe devices such as solar cells where heat dissipation is a concern. Perhaps even more interesting, we show that thermally evapo- rated SnSe thin films, due to their inherent nanostructuring, exhibit extremely low thermal conductivity, substantially below that of the a-axis of the single crystal. Moreover, we demonstrate for the first time in the research literature, a thermally evaporated, thin film, SnSe thermoelectric generator. In this study, we characterize the thermoelectric and material properties of SnSe thin films over a wide range of temperatures. Reactive evaporation was shown to produce a high Seebeck coefficient at low temperature, though the thermo- electric properties were poor at room temperature. While the thermal evaporation of SnSe has been conducted before in the literature, this was with a view to photovoltaic applications. Thermal evaporation is a relatively cheap and facile fabrication technique for thin film devices, in contrast to most SnSe fabrication techniques for thermoelectric applications already presented in the literature. In this paper, we investigate the use of thermal evaporation to manufacture thin films of SnSe. ![]() ![]() This has been successfully demonstrated in Si, Bi 2 Te 3, and manganese silicide to achieve improvements in ZT. Another technique that can be used to reduce the thermal conductivity of a material is the introduction of pores into the structure. showed the fabrication of compressed pellets comprised of porous SnSeS nanosheets with a ZT of 0.12 at room tem- perature. ![]() The lowest thermal conduc- tivity measured is 0.120 W m −1 K −1, this is seen at 200 K. used pulsed laser glancing-angle deposition to grow thin films of SnSe, however did not report a ZT value due to measurements of electrical and thermal properties being on perpendicular planes. on nanostructured SnSe and SnSe-based materials to reduce the thermal conductivity (κ) are scarce in the litera- ture. ![]()
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